Known in particular in metering pump units are toothed gearings that do not transfer a continuous drive movement, but are rather set in motion incrementally, for example via a stepping motor, so that they can controllably execute individual conveying strokes. As a result, the gearing experiences alternating loads or torques, which given the clearance between the individual toothed wheels can lead to an undesirable generation of noise. To avoid this, it has previously been known in such metering pump units to use a gearing with a toothed belt, wherein the toothed belt serves as an attenuator in the gearing. However, the disadvantage to the above is that it increases the size of the gearing, in addition to which a tensioning device must be provided for the toothed belt, and such a toothed belt is subject to wear.